PRELIM LEC: Quality Assurance (TRANSES) Flashcards
TRANSES AND NOTES
1
Q
Overall program that ensures that the final
results reported by the laboratory are correct
A
Quality Assurance
2
Q
It is concerned with all factors that affect the test results from preanalytic, analytic and post-analytic phases
A
Quality Assurance
3
Q
System of ensuring accuracy and precision in the lab
A
Quality Control
4
Q
Process of ensuring that analytical results are correct
A
Quality Control
5
Q
QC samples are measured periodically in the
same manner as clinical samples
A
Quality Control
6
Q
Objectives of Quality Control:
A
- To check the stability of the machine
- To check the quality of the reagent
- To check for technical/clerical error
7
Q
Types of Quality Control:
A
Intralab
Interlab
7
Q
AKA Internal Quality Control
A
Intralab
8
Q
Analyses of control samples
together with patient specimens
A
Intralab
9
Q
Important in daily monitoring
A
Intralab
10
Q
AKA External Quality Control
A
Interlab
11
Q
Involves proficiency testing
programs
A
Interlab
12
Q
Ex.: National External Quality
Assessment Scheme (NEQAS)
A
Interlab
13
Q
Under RIPN
A
Interlab
14
Q
Sends out specimen to labs to test, results are sent back, and results are compared
A
Interlab
15
Q
Characteristics of an Ideal QC Material
A
- With known analyte concentrations
- Inexpensive and stable for long periods
- No communicable diseases
- No matrix effect
- Convenient packaging for easy dispensing and storage
- Resembles human sample
16
Q
Maintain long-term accuracy of
methods
A
Interlab
17
Q
TYPES OF REAGENTS
A
- Reagent Blank
- Standard
- Control
18
Q
Value will tell the conc. of the
unknown
A
Standard
18
Q
Reagent without any analyte
added
A
Reagent Blank
19
Q
Most specific analytical solution
A
Standard
20
Q
Only one analyte
A
Standard
21
Q
Resembles patient sample
A
Control
22
Q
Value will determine accuracy and
precision
A
Control
23
Many analyte
Control
23
Done on sick or ill individuals
Basis for treatment
More accurate, more expensive
Diagnostic Test
24
Done on apparently healthy
individuals
Not a basis for treatment
Less accurate, less expensive
Screening Test
25
QUALITY CONTROL PARAMETERS:
Validity
26
Refers to how well the test measures what it is supposed to measure.
Validity
27
It refers to the accuracy of the test, meaning how close the result is to its true value.
Validity
28
Refers to how well the test performs in use over time
Reliability
29
It refers to the precision of the test, meaning how close are the results of a test on repetition or how close the values are from one another.
Reliability
30
Indicating a person has the
disease when, in fact, he or she
does
True positive (TP)
31
Indicating a person does not have
the disease when, in fact, he or she
does
False negative (FN)
31
Indicating a person has the
disease when, in fact, he or she
does not
False positive (FP)
32
Indicating a person does not have
the disease when, in fact, he or she
does not
True negative
(TN)
33
Ability of test to detect the smallest amount of
analyte
SENSITIVITY
34
Ability of test to identify correctly those who
have the disease (a) from all individuals with
the disease (a+c)
Diagnostic Sensitivity
35
Diagnostic Sensitivity FORMULA:
[TP / (TP + FN)]
36
Ability of test to detect substances without interferences
SPECIFICITY
37
Ability of the test to identify correctly those
who do not have the disease (d) from all
individuals free from the disease (b+d)
Diagnostic Specificity
38
Diagnostic Specificity FORMULA:
[TN / (TN + FP)]
39
Middle value
Median
40
Measure of central
tendency
Mean
41
Most frequent value
Mode
42
Index of precision
Coefficient of
Variation
42
Highest value – lowest value
Range
43
Measures of dispersion
Standard Deviation
and Variance
44
Predictable errors; an error that is constant
when measurements are made under the
same conditions
SYSTEMATIC ERRORS
45
SYSTEMATIC ERRORS 2 TYPES:
Constant error & Proportional error
46
SYSTEMATIC ERRORS Causes:
deterioration of reagents, improperly
made standard solutions, contaminated
solutions, calibration problems, failing
instrumentation
47
Unpredictable errors; often due to instrument,
operator, and environmental conditions
RANDOM ERRORS
48
RANDOM ERRORS CAUSES:
pipetting error, mislabeling of samples, temperature fluctuation, improper
mixing of sample and reagent
48
the most
commonly used histogram in QC
LEVEY-JENNINGS CHART
49
A histogram is/are sheets of rectangular
coordinate graphing paper where data for
sequential analysis are plotted to locate the
source of error
LEVEY-JENNINGS CHART
50
Results from QC fall within the
confidence limit
In Control
51
The values of the control fall
outside the confidence limit
Out of Control
52
Formed by the control that continue to
either increase or decrease for a period of 6 or more consecutive days
Trend
53
Formed by the control that distribute
themselves on one side (above or below) of the mean, with no tendency toward either a
consistent fall or rise
Shift
54
Values which are far from the main
set of values due to wild errors
Outlier/s
55
is a “multi-rule” system
Wesguard Multirule System
56
Developed by Dr. James O. Westgard
Wesguard Multirule System
57
Based on statistical concepts which is a
combination of decision criteria or rules to
assess if a system is in control
Wesguard Multirule System
58
Violated if the IQC value exceeds the mean by ±2SD
1 2s
59
Violated when the IQC value exceeds the mean by
±3SD
1 3s
60
Violated when two consecutive IQC values exceed the mean on the same side of the mean by ±2SD
2 2s
61
Violated if four consecutive IQC values exceed the same limit (mean ± 1SD)
4 1s
61
Violated when one control exceeding the +2s and
another exceeding the -2s
R 4s
62
Violated when 10 consecutive IQC values are on the same side of the mean or target value
10x
63
How close the measured value is to the true
value due to systematic error, which can be
either constant or proportional
Accuracy
64
➔ AKA Linear or Dynamic Range
➔ Range of analyte concentrations that can be directly measured without dilution,
concentration, or other pretreatment
Analytic Measurement Range (AMR)
65
➔ AKA Cross-reactivity
➔ Ability of a method to detect only the analyte it is designed to determine
Analytic Specificity
66
Ability of a method to detect small quantities
or small changes in concentrations of an
analyte
Analytic Sensitivity
67
Difference between the true value and the measured value
Bias
68
Range of analyte that a method can
quantitatively report, allowing for dilution,
concentration, or other pretreatment used to
extend AMR
Clinically Reportable Range (CRR)
69
Type of systematic error in the sample
direction and magnitude; the magnitude of
change is constant and not dependent on the
amount of analyte
Constant Error
70
Effect of a compound/s on the accuracy of the
detection of a particular analyte
Interference
71
Substances that cause interference
Interferents
72
Lowest amount of analyte accurately detected
by a method
Limit of Detection
73
Lowest amount of analyte that can be
reported while achieving a precision target
(e.g. lowest concentration at which a CV of 10% may be achieved)
Limit of Quantitation
74
Body component (e.g. fluid and urine) in which
the analyte is to be measured
Matrix
75
Dispersion of repeated measurements about
the mean due to analytic error
Precision
76
Type of systematic error where the magnitude
changes as a percent of the analyte present,
error dependent on analyte concentrations
Proportional Error
77
➔ Error varies from sample to sample
➔ Causes include instrument instability,
temperature variations, reagent variation,
handling techniques, and operator variables
Random Error
78
➔ Ability of an analytic test to measure a known amount of analyte
◆ A known amount of analyte is added
to real sample matrices
Recovery
79
80
➔ Refers to the difference between the
measured value and the mean expressed as a
number of SDs
➔ An SDI = 0: value is accurate or in 100%
agreement
➔ An SDI = 3: 3 SDs away from the target (mean) and indicates inaccuracy
➔ SDI may be positive or negative
Standard Deviation Index
81
82
Error always in one direction (may be constant or proportional
Systematic Error
83
Random error + Systematic error
Total Error
